The invention relates to a laser sensor holder apparatus, and in particular to such an apparatus for use in conjunction with power monitoring of laser beams, and to a method of measuring the power of a laser beam.
Laser power units, for example laser power units which emit laser beams for use in lithographic plate imprinting, are frequently used in situations in which beam strengths are occasionally varied and need to be checked prior to use or in which the beam strength needs to be regularly measured and precisely calibrated. There is therefore a need for a means of regular monitoring and calibrating.
Suitable power sensors are usually employed in order to monitor the strength of the beam for each application and check that the beam has been calibrated to within acceptable limits. Calibration may involve taking multiple readings, interspersed with computer controlled adjustment of the beam strength.
In known arrangements, sensors employed to monitor and calibrate the beams are usually hand-held, requiring a user to stand in front or to one side of the laser power unit, holding the sensor in the path of the beam. There are a number of inherent disadvantages with this method of monitoring.
One disadvantage is that the user will never be able to keep the sensor in a totally stationary position and therefore, for any one sensor reading, there may be fluctuations as the sensor moves from the centre of the beam to its periphery and back again.
A second disadvantage is that after each sensor reading the user must move to a computer terminal to input data and adjust the power output of the laser up or down accordingly before returning to the beam area once more to check the actual effect of the adjustments. When the user returns to the sensor to take the next reading, he will not be able to hold the sensor in exactly the same position as in the previous reading. Even if the laser power has not been changed the new position of the sensor, coupled with the instability of the hand-held sensors position, can lead to significantly erroneous readings.
The need for the user to undergo repetition of sensor reading, moving to the computer terminal, inputting data and returning to the sensor, means valuable time is wasted. Indeed for many applications, calibration in this manner can take up to half a day to complete.
As the user must hold sensors of known arrangement in his hand, there is a high risk that the laser beam could come into contact with the skin of his hand. Some applications require the use of powerful (class 4) lasers which would cause serious bums and tissue damage if there is any beam to skin contact.
It is therefore a first object of the present invention to provide a laser power sensor holder which is designed to be coupled with a laser power sensor and secured in the path of a beam.
It is further an aim of preferred embodiments of the present invention to provide a sensor holder which can be adjusted, when attached to a laser power unit, such that the sensor element of the coupled sensor is stationary and exposed to the whole cross-section of the beam and is thereby eliminating inaccurate readings caused by the sensor missing parts of the beam caused by movement of the sensor during operation.
It is another aim of preferred embodiments of the present invention to provide a sensor holder which permits the elimination of time-wasting caused by repeated movement between the sensor and a power controller of the laser.